Redmine

I have an error on /projects/s-org_ipd/issues/gantt

system info

Environment:
  Redmine version                3.3.1.stable
  Ruby version                   2.1.5-p273 (2014-11-13) [i386-linux-gnu]
  Rails version                  4.2.7.1
  Environment                    production
  Database adapter               Mysql2
SCM:
  Git                            2.1.4
  Filesystem
Redmine plugins:
  no plugin installed

30162 Started GET "/projects/s-org_ipd/issues/gantt" for ███.███.███.███ at █████████ ████████ +████
30163 Processing by GanttsController#show as HTML
30164   Parameters: {"project_id"=>"s-org_ipd"}
30165   Current user: ███████████ (id=██)
30166   Rendered queries/_filters.html.erb (13.5ms)
30167   Rendered gantts/show.html.erb within layouts/base (90.5ms)
30168 Completed 500 Internal Server Error in 434ms (ActiveRecord: 102.3ms)
30169
30170 ActionView::Template::Error (undefined method `-@' for Sat, 01 Oct 2016:Date):
30171     107: ^M
30172     108:   # Width of the entire chart^M
30173     109:   g_width = ((@gantt.date_to - @gantt.date_from + 1) * zoom).to_i^M
30174     110:   @gantt.render(:top => headers_height + 8,^M
30175     111:                 :zoom => zoom,^M
30176     112:                 :g_width => g_width,^M
30177     113:                 :subject_width => subject_width)^M
30178   lib/redmine/helpers/gantt.rb:575:in `coordinates'
30179   lib/redmine/helpers/gantt.rb:330:in `line'
30180   lib/redmine/helpers/gantt.rb:293:in `line_for_project'
30181   lib/redmine/helpers/gantt.rb:258:in `render_object_row'
30182   lib/redmine/helpers/gantt.rb:216:in `render_project'
30183   lib/redmine/helpers/gantt.rb:205:in `block in render'
30184   app/models/project.rb:809:in `block in project_tree'
30185   app/models/project.rb:805:in `each'
30186   app/models/project.rb:805:in `project_tree'
30187   lib/redmine/helpers/gantt.rb:203:in `render'
30188   app/views/gantts/show.html.erb:110:in `_app_views_gantts_show_html_erb___499571926_101375260'
30189   app/controllers/gantts_controller.rb:43:in `block (2 levels) in show'
30190   app/controllers/gantts_controller.rb:42:in `show'
30191   lib/redmine/sudo_mode.rb:63:in `sudo_mode'